Why This Route Works
Barcelona, Madrid, and Seville show three different sides of Spain: Mediterranean architecture and beaches, capital-city museums and nightlife, and Andalusian courtyards, flamenco, and warm old streets. High-speed rail makes the route manageable if you avoid too many extra stops.
Barcelona
Use Barcelona for Gaudi architecture, markets, neighborhoods, museums, and a beach-adjacent city rhythm. Book Sagrada Familia and other headline sights ahead, then leave open time for wandering and food.
Madrid
Madrid works as the route's practical center. It has major museums, royal sights, tapas areas, parks, and strong rail links. It can also support day trips, but do not add too many if this is a short first visit.
Seville
Seville changes the mood with orange trees, palace courtyards, flamenco, tapas, and slower evenings. It can be hot, so plan outdoor sightseeing early or late and use afternoons carefully.